Let's have the exact number of the macerator. Close just ain't good enough when we're looking for the specs of the pump.
macerator doesn't have enough oumph
- Thread starter sabbatical88
- Start date
@JamesG161 @Ralph Johnstone, the Jabsco pump in use is the 18590-0000, which is 12V. Agian, my bad for posting the wrong model number earlier. Experiments yesterday:
- cut another 1/2 inch off of the virtical host to the macerator, reinstall. Thought lowering macerator might help get suction. No change.
- veriried 12+ volts across macerator leads under operation. (brought 12.8V directly to the leads with a portable battery). No change
- swapped out jabsco with amarine macerator. No change.
- verified the outbound hose to the thruhull is clear (remove hose from macerator, attach to shopvac and blow, verlfy lots of bubbles beside boat).
- tried running macerator while using a hose into the deck plate, hoping to get the pump to prime. No change.
Next steps:
- buy some hose and connect to macerator in and out. Try pumping directly from 4" plate installed in the tank. See if I can pump from a height >= where the macerator currently mounted. This will tell me if it is truely both pumps are bad, or if there is something in the piping from tank to macerator (although already somewhat confirmed ok since I could pump out from deck plate.)
thoughts and suggestions appreciated.
- cut another 1/2 inch off of the virtical host to the macerator, reinstall. Thought lowering macerator might help get suction. No change.
- veriried 12+ volts across macerator leads under operation. (brought 12.8V directly to the leads with a portable battery). No change
- swapped out jabsco with amarine macerator. No change.
- verified the outbound hose to the thruhull is clear (remove hose from macerator, attach to shopvac and blow, verlfy lots of bubbles beside boat).
- tried running macerator while using a hose into the deck plate, hoping to get the pump to prime. No change.
Next steps:
- buy some hose and connect to macerator in and out. Try pumping directly from 4" plate installed in the tank. See if I can pump from a height >= where the macerator currently mounted. This will tell me if it is truely both pumps are bad, or if there is something in the piping from tank to macerator (although already somewhat confirmed ok since I could pump out from deck plate.)
thoughts and suggestions appreciated.
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 22,076
As Ralph suggested earlier, is there an air leak at the deck fitting. In your first post you said the pump worked fine in your garage. Maybe all you need is a 50 cent o-ring. I had trouble getting suction pumping-out last summer and it turn out to be a bad connection at a coupler. You'd be surprised how a small leak can kill the vacuum. (I know I shouldn't use a coupler but it's a beneteau with those pita metric deck fittings-it's on my winter todo list)
@jssailem, Not sure what you mean by "you pump out using your macerator"- yes obviously, or from the deck plate. The 4" hole is in the top of the tank. The effluent is (or should be) pumped from the bottom.
@TimFromLI, I did replace the O ring at the deck, but I'll check it again. I wish I had enough space to put in a simple PVC ball valve just on the deck side of the "T".
@TimFromLI, I did replace the O ring at the deck, but I'll check it again. I wish I had enough space to put in a simple PVC ball valve just on the deck side of the "T".
Hi John. The diagram that the PO provided indicates the same setup as on our boat. One standpipe in the waste tank is used to empty the tank either through the deck pump out fitting or the macerator overboard discharge pump. The hose from the standpipe connects to a wye/tee fitting where one hose goes to the deck, the other to the macerator. He said the system pumps out just fine through the deck fitting, so, unless there is a blockage/air leak somewhere in the system, the macerator should work as well.
Our 1991 original Jabsco macerator overboard pump always works. A small air leak in the system can prevent the macerator from priming, such as a small one upstream, either in the tank standpipe, deck fitting cap, etc. That small air leak might not be enough to prevent the deck pump out from working, but would the macerator pump, as most pump out stations provide a pretty strong evacuation vacuum. Certainly a puzzle.
Looking at the limit for self priming, this is 0.6m = 23.6 inches. And usually this is wishful thinking for an impellor type pump on the part of the manufacturer. You mentioned that the macerator sits about 18-24" above the top of the tank but how far above the water line in the tank is the real question to ask. If the tank water level is 10" below the top of the tank, you may now be trying to pull something up to 30" which the pump just can't do. I think you may be a little too high for the pump to lift in order to prime the pump.
Unfortunately, both the "T" and the macerator will have to be lowered to just above the level of the top of the tank for this to work. Calculate if you have a small enough suction head when the tank is near empty for this to work,
This could easily be the issue and might be worse than @Ralph Johnstone suggests as the pump draws from the bottom of the tank. It will get a slight boost when the tank is full because of the head in the dip tube, however, as the level drops, it loses that head and has to lift ever higher which it can't do. Add to that the back pressure from the pump being below the waterline and it will just sit there spinning its macerator.
From the manual the 18590-0000 is self priming to 4’ when impeller is dry, 5’ when wet.
Even a small air leak will prevent most pumps from priming. Check that ALL connections are fully tight for it to operate. As a test you could swap the T fitting for an elbow, or even replace the suction hose between the macerator and the tank with a single direct piece to see if it operates normally in that mode.
As Jim mentioned above, a plugged vent will prevent pumping, but would also likely be evident when using the deck pump out.
Even a small air leak will prevent most pumps from priming. Check that ALL connections are fully tight for it to operate. As a test you could swap the T fitting for an elbow, or even replace the suction hose between the macerator and the tank with a single direct piece to see if it operates normally in that mode.
As Jim mentioned above, a plugged vent will prevent pumping, but would also likely be evident when using the deck pump out.
In your drawing, what? The deck pumpout through the macerator? I gotta say no way can that be factory. Deck pump out completely off of the macerator line. Comes directly out of the tank. And dont trust those standard layouts in the manuals. My boat is completely different than what the book shows. My issue was similar, forward head, stock macerator would intermittently just bog down like it was clogged. I tried the screwdriver on the top of it to get it to turn. I took the lines off. My forward head has an elbow at the bottom, goes two feet to the pump, up and hook down then out the thru at bottom of hull. Drove me nuts cuz I couldnt solve it. More powerful macerator... decent results but. So this is witchcraft BUT, I prime the macerator with a few bumps (3 0r 4) of the pump out button for about a second each. My theory is that doing this brings the sludge up the race of the lines to the pump. However it works, it works. Your other option is to swap out and put a T series pump in.
Good luck
@Rick, deck pumpout wasn't 'through' the macerator, but would suck below it through the 'T'. I drew it as it is in the boat. I dropped in a new jabsco 18590-2094 and it works for now at least. I guess (a) the the old jabsco with the rebuild kit and (b) the aMarine macerator were both insufficient. Maybe they were run dry too long. Maybe there is a very small airleak somewhere. Maybe it's a crap design and there really should have by a y valve instead of the T and maybe I could lower the macerator a little more to the waterline. At least now that I have a 4" 'viewport' into the top of the tank I can see what is happening and not overrun the pump. Thanks @Terry Cox @Ralph Johnstone @Richard19068 and everyone for the help. I have a lot better understanding of the issue and a working (for now) system.
Thank you for the good news. Hunter located our macerator pump below the waste tank. It would always change to a slightly higher pitched sound when the tank was pumped empty.
Last edited:
As mentioned by @Terry Cox , there is a very distinct rise in the pitch of the motor when the last drop of
is discharged.
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 22,076
Would this indicate that the pump is now just pumping holding tank farts and all the solid’s are gone?there is a very distinct rise in the pitch of the motor when the last drop of
Yup. Like most pump motors of this type, the RPM changes slightly when a load is removed. And I do mean several loads of
.
Are you insinuating that there is a difference in density between holding tank farts and general run of the mill air ? How does the pump know this ? Please quote your source.